When someone sits without someone else, he should ask his permission to leave
Abu Burda ibn Abi Musa said, "I sat with 'Abdullah ibn Sallam. He said, 'You have sat down with us, but now it is time for us to leave.' I said, 'If you like.' He got up and I followed him to the door."
حَدَّثَنَا عِمْرَانُ بْنُ مَيْسَرَةَ عَنْ حَفْصِ بْنِ غِيَاثٍ عَنْ أَشْعَثَ عَنْ أَبِي بُرْدَةَ بْنِ أَبِي مُوسَى قَالَ جَلَسْتُ إِلَى عَبْدِ اللهِ بْنِ سَلاَّمٍ فَقَالَ إِنَّكَ جَلَسْتَ إِلَيْنَا وَقَدْ حَانَ مِنَّا قِيَامٌ فَقُلْتُ فَإِذَا شِئْتَ فَقَامَ فَاتَّبَعْتُهُ حَتَّى بَلَغَ الْبَابَ